Embolic protection device

ABSTRACT

An embolic protection device has a collapsible filter element ( 105 ) mounted on a carrier such as a guidewire ( 101 ). The filter element ( 105 ) collapses into the outer end of a catheter ( 118 ) for deployment and retrieval through a vascular system of a patient. The filter element ( 105 ) has a collapsible filter body with a proximal inlet end and a distal outlet end. The proximal inlet end has inlet openings sized to allow blood and embolic material enter the filter body. The outlet end has outlet openings which allow through passage of blood but retain embolic material within the filter body. After use, the catheter ( 118 ) is movable along the guidewire ( 101 ) to engage the proximal end of the filter element and close the inlet openings before sliding over the filter element from the proximal end to the distal end to progressively collapse the filter body on the guidewire ( 101 ) for retrieval. The filter element ( 105 ) may conveniently be mounted on a tubular sleeve ( 104 ) which is slidable and rotatable on the guidewire ( 101 ) between spaced-apart slops ( 106, 120 ) on the guidewire ( 101 ) which allows some manipulation of the guidewire independently of the filter when the filter is in use.

This is a continuation of U.S. application Ser. No. 10/410,606, filedApr. 10, 2003, now abandoned which is a continuation of U.S. applicationSer. No. 10/058,828, filed Jan. 30, 2002, which is a continuation ofU.S. application Ser. No. 09/921,596 filed Aug. 6, 2001, now U.S. Pat.No. 6,432,122, which is a continuation of U.S. application Ser. No.09/188,472 filed Nov. 9, 1998, now U.S. Pat. No. 6,336,934. The contentof each of these applications is incorporated herein by reference.

INTRODUCTION

The invention relates to an embolic protection device.

The term “STROKE” is used to describe a medical event whereby bloodsupply to the brain or specific areas of the brain is restricted orblocked to the extent that the supply is inadequate to provide therequired flow of oxygenated blood to maintain function. The brain willbe impaired either temporarily or permanently, with the patientexperiencing a loss of function such as sight, speech or control oflimbs. There are two distinct types of stroke, haemorrhagic and embolic.This invention addresses embolic stroke.

Medical literature describes carotid artery disease as a significantsource of embolic material. Typically, an atherosclerotic plaque buildsup in the carotid arteries. The nature of the plaque variesconsiderably, but in a significant number of cases pieces of the plaquecan break away and flow distally and block blood now to specific areasof the brain and cause neurological impairment. Treatment of the diseaseis classically by way of surgical carotid endarterectomy whereby, thecarotid artery is cut and the plaque is physically removed from thevessel. The procedure has broad acceptance with neurologicalcomplication rates quoted as being low, somewhere in the order of 6%although claims vary widely on this.

Not all patients are candidates for surgery. A number of reasons mayexist such that the patients could not tolerate surgical intervention.In these cases and an increasing number of candidates that are surgicalcandidates are being treated using transcatheter techniques. In thiscase, the evolving approach uses devices inserted in the femoral arteryand manipulated to the site of the stenosis. A balloon angioplastycatheter is inflated to open the artery and an intravascular stent issometimes deployed at the site of the stenosis. The action of thesedevices as with surgery can dislodge embolic material which will flowwith the arterial blood and if large enough, eventually block a bloodvessel and cause a stroke.

It is known to permanently implant a filter in human vasculature tocatch embolic material. It is also known to use a removable filter forthis purpose. Such removable filters typically comprise umbrella typefilters comprising a filter membrane supported on a collapsible frame ona guidewire for movement of the filter membrane between a collapsedposition against the guidewire and a laterally extending positionoccluding a vessel. Examples of such filters are shown in U.S. Pat. No.4,723,549, U.S. Pat. No. 5,053,008, U.S. Pat. No. 5,108,419 and WO98/33443. Various deployment and/or collapsing arrangements are providedfor the umbrella filter. However, as the filter collapses, the capturedembolic material tends to be squeezed outwardly towards an open end ofthe filter and pieces of embolic material may escape from the filterwith potentially catastrophic results. More usually, the filter umbrellais collapsed against the guidewire before removal through a catheter orthe like. Again, as the filter membrane is collapsed, it will tend tosqueeze out the embolic material. Further, the umbrella filter isgenerally fixed to the guidewire and any inadvertent movement of theguidewire during an interventional procedure can dislodge the filter.

The present invention is directed towards overcoming these problems.

There is a need for an embolic protection device which will overcomethis problem.

STATEMENTS OF INVENTION

According to the invention, there is provided an embolic protectiondevice comprising:

-   -   a collapsible filter element mounted on a filter carrier for        delivery through a vascular system of a patient,    -   the filter element being movable between a collapsed stored        position against the filter carrier for movement through the        vascular system, and an expanded position for occluding a blood        vessel such that blood passing through the blood vessel is        delivered through the filter element,    -   the filter element comprising a collapsible filter body having        an inlet end and an outlet end,    -   the inlet end of the filter body having one or more inlet        openings sized to allow blood and embolic material enter the        filter body,    -   the outlet end of the filter body having a plurality of outlet        openings sized to allow through passage of blood but to retain        undesired embolic material within the filter body,    -   means for closing the inlet openings at the inlet end of the        filter body, and    -   means for collapsing the filter body on the support.

Advantageously, the inlet openings in the filter are closed before thefilter is collapsed ensuring retention of all embolic material withinthe filter element.

In a particularly preferred embodiment of the invention, the means forclosing the inlet comprises:—

-   -   a tubular filter retrieval device having an open distal end for        reception of the filter element,    -   said distal end being engagable with a proximal inlet end of the        filter body to close the inlet openings and being slidable over        the filter body from the inlet end to the outlet end to        progressively collapse the filter body on the filter carrier and        receive the filter body within the retrieval device.

Conveniently, the retrieval device which may be a catheter or pod or thelike which engages and collapses the filter element firstly closing theinlet openings to prevent any escape of embolic material and thencollapsing the remainder of the filter, being slid from the proximal endover the filter to the distal end of the filter.

In a particularly preferred embodiment, the collapsible filter elementis slidably mounted on the filter carrier between the a pair ofspaced-apart stops on the filter carrier for axial movement of thefilter element along the filter carrier between the stops.

Advantageously, the filter carrier which may for example be a guidewirecan be moved independently of the filter element and thus accidentalmovement of the guidewire is accommodated without unintentionally movingthe filter, for example, during exchange of medical devices.

In a further embodiment, the filter element is rotatably mounted on thefilter carrier.

In a preferred embodiment, a sleeve is slidably mounted on the filtercarrier between the stops, the length of the sleeve being less than thedistance between the stops, the filter element being mounted on thesleeve.

In a particularly preferred embodiment, the filter element comprises:—

-   -   a collapsible filter net mounted on the filter carrier,    -   the filter net being movable between a collapsed stored position        against the filter carrier and an expanded position extending        outwardly of the filter carrier for deployment across a blood        vessel.

Preferably, the tubular fitter retrieval device comprises a catheterslidable along the filter carrier, an open distal end of the catheterforming a housing for reception of the filter element.

In another embodiment, a proximal inlet end of the filter body is fixedto the filter carrier and a distal end of the filter body is slidablymounted on the filter carrier, although this arrangement may bereversed.

In a further embodiment, the distal end of the filter body is attachedto a collar which is slidable along the fitter carrier.

In a preferred embodiment, a filter support frame is mounted on thefilter carrier, the support frame being movable between a collapsedposition along the filter carrier and an extended outwardly projectingposition to support the filter body in the expanded position.

In another embodiment, the filter support frame is fixed on the filtercarrier at a proximal end of the filter body.

Preferably, the filter support frame slidably engages the filter carrierat a distal end of the filter body. Ideally, the filter support frame isbiased into a normally extended position.

In a further embodiment, a circumferential groove is provided in thefilter body intermediate the ends of the filter body.

In another embodiment, a guide olive is provided on the filter carrierdistally of the filter body, the guide olive having a cylindrical bodywith a tapered distal end, the cylindrical body being engagable within adistal end of a deployment catheter, said tapered distal end projectingoutwardly of the deployment catheter to provide a smooth transitionbetween the catheter and the filter carrier.

In a further embodiment, the net is gathered into the filter carrier ateach end of the net.

In another embodiment of the invention, there is provided an embolicprotection device comprising a filter element for placing in a desiredposition, the filter element providing a pathway for blood and havingmeans for capturing, retaining and removing undesired embolic material.

In one embodiment of the invention, the pathway has means forconstricting flow to capture undesired embolic material.

In another embodiment of the invention, the filter has a proximal endand a distal end, openings in the proximal end being larger thanopenings in the distal end, the proximal end openings being sized toallow the flow of blood and embolic material to enter the filter elementand the distal end openings being sized to allow the flow of blood whilecapturing undesired emboli within the filter element.

In a further embodiment of the invention, the filter element includesstorage means to store captured undesired embolic material in the filterelement. Preferably, the storage means comprises additional storagepathways within the filter element. Preferably, the filter elementdefines a three dimensional matrix.

In another embodiment of the invention, the filter element is of apolymeric porous structure. In a further embodiment of the invention,the matrix comprises a porous structure dimensioned to entrap embolicmaterial which typically ranges in size from about 100 microns to 3500microns. In a still further embodiment of the invention, the filterelement is compressible and/or foldable for loading into a deliverydevice to deliver the filter element to a desired location in thecompressed or folded state.

In one embodiment of the invention, the filter element has materialremoved from its structure to aid compressibility.

In another embodiment of the invention, the filter element has materialremoved from its structure to provide specific sizing in relation to thesize of embolic material to be trapped.

In a further embodiment of the invention, the filter element haspathways through the filter body that are inter-linked such that theflow rate through the filter may be tailored.

In another embodiment of the invention, the filter element has a distalend which is tapered such that there is a smooth transition in lateralstiffness to improve the manoeuvrability of the filter element in thevascular system.

In a further embodiment of the invention, the filter element has a softdistal portion to aid in atraumatic transport through the vascularsystem. Preferably, the filter element has circumferential grooves toreduce the lateral flexibility of the filter element.

In one embodiment of the invention, the filter element has a taperedproximal end to facilitate retrieval by a removal catheter.

In another embodiment of the invention, the filter element has inletholes that close on pulling back into a retrieval catheter to ensureretention of any collected emboli.

In a further embodiment of the invention, the filter element has outletopenings sized to capture embolic material of a size large enough toimpair the function of the organ receiving the blood downstream of thefilter body element. Preferably, the filter element is sized to captureembolic material of a size greater than 100 microns. Most preferably,the filter element is sized to capture embolic material of a sizegreater than 200 microns. Most preferably, the filter element is sizedto capture embolic material of a size greater than 500 microns.

In one embodiment of the invention, the filter element is sized forcomplete coverage of a vessel cross-section that allows passage of bloodand blood components.

In a still further embodiment of the invention, there is provided adevice having means for placing over a medical guidewire.

In another embodiment of the invention, there is provided a device whichmay be placed under a balloon or stent delivery catheter.

In a further embodiment of the invention, there is provided a devicehaving means for insertion through, femoral, brachial, radial,subclavian or other arterial puncture by means of a transcatheterapproach.

In one embodiment of the invention, there is provided a device forprotection of neurological function which is inserted for the durationof a surgical intervention at or near the site of surgical opening.

It is envisaged that two devices could be used bi-laterally in left andright carotid arteries allowing sufficient cerebral blood flow tomaintain neurological function during procedures with a high risk ofgenerating clot such as electrophysiological treatment of coronaryarrhythmias.

In a further embodiment of the invention, there is provided a deviceincluding a delivery catheter in which an external sheath is engagablewith the filter element or filter carrier to provide push duringdelivery and is removable to allow maximum space in the vascularcross-section during an interventional procedure.

In one embodiment of the invention, the external sheath is joined to thefitter element or filter carrier by a joining means. The joining meansmay be a removable shrink tube or a removable clip. Preferably thejoining means is a compression connector such as a Touhy Borst adapter.

In another embodiment of the invention, the delivery catheter has acentral lumen for at least part of it's length to allow it to track overa steerable guidewire.

In a further embodiment of the invention, the external sheath issufficiently long to extend to the outside of the vasculature and ismovable proximally to release the filter element from the catheter.

In one embodiment of the invention, the delivery catheter has anexternal covering which extends beyond the push element to define afilter retention sleeve.

In another embodiment of the invention, the delivery catheter has aspring component with a localised stepwise increasing pitch to alterstiffness characteristics to suit the target vasculature.

In a further embodiment of the invention, the delivery catheter has aspring component with a localised gradually increasing pitch to alterstiffness characteristics to suit the target vasculature.

In one embodiment of the invention, the filter element is mounted on acollapsible support structure which is movable between a collapsedposition for deployment and an extended in-use position, means beingprovided for retaining the support structure in the collapsed position.Preferably, the support structure comprises support arms. Preferably,the support arms are formed from a shape memory or elastic memorymaterial. Most preferably, the support arms are formed from Nitinol.

In one embodiment of the invention, the support arms are configured toopen co-axially with the filter carrier such that they may be restrainedfor removal by pulling the filter element proximally into anappropriately dimensioned sheath.

In another embodiment of the invention, the filter element has anassociated support structure with a pre-shaped spiral arrangement suchthat it provides radial support to the filter element.

In a further embodiment of the invention, the filter support structureis adapted to fold into the collapsed position when pulled into aretrieval catheter.

In one embodiment of the invention, the filter element comprises aflexible shaped polymeric component.

In another embodiment of the invention, the shaped polymeric componentis constructed such that fluid flow through the component assists inopening the component from the collapsed position.

In a further embodiment of the invention, the shaped polymeric componentis flexible and opens to make circumferential contact with the vesselwall by way of using the pressure drop across the exit filter face.

In a further embodiment of the invention the filter element is mountedon a guidewire such that the guidewire has freedom to rotate and/or moveaxially independently of the filter. More preferably the wire hascomplete freedom to rotate independently of the filter and has limitedaxial movement. The limit of axial movement is determined by stopsmounted on or connected to the wire. Ideally the wire can move 100 mm inthe axial direction independent of the filter. More ideally the wire canmove less than 50 mm independently of the filter. This embodimentfacilitates the maintenance of filter position during the exchange ofcatheters and permits the steering of the wire independent of thefilter.

In a further embodiment of this invention the filter element is bondedto the filter mount at its proximal end and its distal end is free tomove relative to the filter mount and proximal bond so as to aid thecollapse of the filter for deployment.

In a further embodiment of the invention the filter element is taperedover part or all of its length such that it is accurately sized to thevessel over some portion of its length.

In a further embodiment of the invention the shaped polymeric componentcontains one or more circumferential grooves along its body to maintainthe circular shape of the filter element in an under sized artery.

In one embodiment of the invention, the filter element is directlybonded onto a steerable medical guide wire incorporating a slidablesheath that is movable to deploy the filter.

In another embodiment of the invention, there is provided a deviceincorporating a medical guidewire with a flexible segment of wire distalto the filter so as to provide steerability of the wire particularlyprior to it being deployed.

In a further embodiment of the invention, there is provided a deviceincorporating a medical guide wire with a soft distal segment so as toprovide a tip section that will be atraumatic.

In a still further embodiment of the invention, there is provided adevice with a porous coating on a distal end of the filter element onlywith a means for opening and closing the filter by slidable motion.

In one embodiment of the invention, the filter element incorporatesproximal tapering such that it may be pulled proximally into a sheathfor removal in order that such pulling action will effectively reducethe diameter of the filter and assist retrieval.

In another embodiment of the invention, the filter element has a porousstructure that can be deployed and closed by way of a slidable motion,the closure thereof caused by way of snap-fit to a protruding rim thatallows the support elements be pulled proximally, thus closing thestructure with the filter membrane attached.

In a further embodiment of the invention, there is provided a devicehaving a filter element which permits the incorporation of a medicalguide wire in the outer wall of the filter element to facilitate theincorporation of large inlet holes on the proximal inlet end of thefilter element.

In one embodiment of the invention, the filter element comprises a meshwork structure with large proximal inlet holes and small distal outletholes wherein the mesh structure is collapsible into a small diameterdelivery catheter and is expandable upon deployment to a shape which isremembered by the mesh structure either through shape memorycharacteristics or elastic memory characteristics.

In another embodiment of the invention, the filter element comprises amesh work structure wherein the expansion of the filter element withinthe vessel causes blood flowing through the vessel to flow through thefilter element due to the filter element engaging with the wall of thevessel to conform to the shape of the vessel bore.

In another embodiment, the filter element comprises a braided fibrousmesh work. Preferably, distal outlet openings are defined by an areaenclosed by a series of crossing interwoven fibres. Larger proximalinlet holes are provided by the convergence of the fibres of the braidinto a few bundles which are mounted to the filter carrier. Preferably,the fibrous meshwork material is an elastic or shape memory materialsuch that it can be collapsed into a delivery catheter and recover itsenlarged shape upon deployment. The fibres of the meshwork are bonded atthe points where they cross one another. The fibres may be made fromeither a polymer or metal or a composite material.

In a further embodiment, the distal end of the filter element has thefacility to move in the axial direction relative to the proximal end ofthe filter element so as to take up the exact shape of the blood vessel.

In a further embodiment, the device has a porous coating on a distal endof the filter element only with means for opening and closing the filterelement by slidable motion. Preferably, the fitter element comprises acollapsible wire frame having a plurality of wires, outer ends of thewires being hingedly mounted on the filter carrier, the wires beinghinged intermediate their ends, at one end the wires being fixed on thefilter carrier and at the other end the wires being mounted on a collarwhich is slidable along the filter carrier, a porous filter mesh beingmounted on the wire frame. An actuating sleeve is slidable over thefilter carrier to push the collar towards the fixed end of the filterelement, and a collapsing device is engagable with the collar to pullback the collar away from the fixed end of the filter element tocollapse the wire frame against the filter carrier for retrieval of thefilter element.

In a still further embodiment of the invention, there is provided afilter retrieval system for use with the device comprising alongitudinal catheter with a radially deformable or elastic tip toassist the pull back of the filter into the tip.

In another embodiment of the invention, there is provided a systemincorporating a filter, a delivery catheter and a retrieval catheter fortemporary filtration of the vascular system during an interventionalprocedure.

In another aspect the invention provides an embolic protection devicecomprising:

-   -   a collapsible filter element mounted on a filter carrier for        delivery through a vascular system of a patient,    -   the filler element being movable between a collapsed stored        position against the filter carrier for movement through the        vascular system, and an expanded position for occluding a blood        vessel such that blood passing through the blood vessel is        delivered through the filter element, a pair of spaced-apart        stops on the filter carrier, the collapsible filter element        being slidably mounted on the filter carrier for axial movement        along the filter carrier between the stops, and means for        collapsing the filter element on the filter carrier.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be more clearly understood from the followingdescription thereof given by way of example only with reference to theaccompanying drawings in which:—

FIG. 1 is a side view of an embolic protection device according to theinvention, in use;

FIG. 2 is a side view of the device of FIG. 1 in a pre-loaded positionfor insertion;

FIG. 3A is a side view illustrating one method of fixing the device tocatheter;

FIG. 3B is a side view of an embolic protection device incorporating thefixing of FIG. 3A;

FIG. 4 is a side view illustrating another method of fixing;

FIG. 5 is an end view of a split collar used in the fixing of FIG. 4;

FIG. 6 is a side view illustrating a further method of fixing;

FIG. 7 is an end view of a jubilee clip used in the fixing of FIG. 6;

FIG. 8 is a side view of one filter element used in the device of theinvention;

FIG. 9 is a side view of another filter element;

FIG. 10 is a side view of the filter element of FIG. 8 being removed;

FIG. 11 is an isometric view of another filter element in an in-useplaced configuration;

FIG. 12 is a side view of the filter element of FIG. 11 in a retractedposition for insertion and withdrawal;

FIGS. 13 to 15 are side views of another filter element in differentpositions;

FIGS. 16 and 17 are side views of part of a further filter element witha snap fit retrieval arrangement;

FIG. 18 is a perspective, partially cross-sectional view of anotherembolic protection device shown mounted in a vessel;

FIGS. 19 a to 19 c are perspective views illustrating the formation of acollapsible filter support for use in the device of FIG. 18;

FIGS. 20 to 22 are perspective views of other filter elements;

FIG. 23 is an elevational view of another filter element;

FIG. 24 is a sectional view taken along the line XXIV-XXIV of FIG. 23;

FIG. 25 is a sectional view taken along the line XXV-XXV of FIG. 23;

FIG. 26 is an enlarged detail view of portion of the filter;

FIG. 27 is an expanded view of the filter element of FIG. 23;

FIG. 28 is a side view illustrating one method in which the substratetubing that the filter element is attached to can run over the primarycrossing guidewire;

FIG. 29 is a side view illustrating the position in which the “olive”component will sit in order to provide a smooth transition between theprimary crossing guidewire and the loading pod;

FIG. 30 is a perspective view of the filter element in its most distalposition;

FIG. 31 is a perspective view of the filter element in its most proximalposition;

FIG. 32 is a perspective view of the filter element when the distal endof the filter is not bonded to the substrate tubing;

FIG. 33 is a side view of a concertina shaped filter; A being when thefilter is deployed and B when the filter is in its loaded shape;

FIG. 34 is a perspective view of the floating distal tip design with aspring element incorporated distal to the floating tip;

FIG. 35 is a side view of another floating distal tip design with aspring incorporated into the distal tip;

FIG. 36 is a side view of the floating distal tip design with the shapememory alloy extending from the proximal end to the distal end;

FIG. 37 is a perspective view of the mesh design incorporating afloating distal tip;

FIG. 38 illustrates perspective views of filter geometries;

FIG. 39 shows a fibrous mesh filter design with fibres woven at thedistal end and converging into a number of bundles at the proximal end;

FIG. 40 is partially sectioned elevational view an embolic protectiondevice according to the invention;

FIG. 41 is a schematic sectional elevational view of the embolicprotection device of FIG. 40; and

FIG. 42 is a detail sectional view of portion of the device of FIG. 40.

DETAILED DESCRIPTION

Referring to the drawings there are illustrated various embolicprotection devices according to the invention. The devices, in general,comprise a fitter element for temporary placing in a desired positionduring a surgical or interventional procedure, typically using aguidewire and catheter. The filter element provides a pathway for bloodand has means for capturing and retaining undesired embolic materialreleased during the surgical procedure. The filter element containingthe retained embolic material is removed when the interventionalprocedure is completed. In this way the patient is protected against therisk of stroke or other complications caused by the release of undesiredembolic material during the procedure.

In one embodiment of the device it will be used in an over the wiretranscatheter configuration. The clinician will cross the lesion with asteerable guidewire. The cerebral protection device will then bethreaded over the guidewire and will be placed distal to the site of thelesion being treated. By means of actuation, or other means, the fitteris deployed into the vessel and will capture emboli that are generatedor dislodged during balloon inflation and stent placement. The deviceconsists of a filter attached to a shaft that can run over the primarycrossing guidewire.

Referring initially to FIGS. 1 and 2 in this case the filter elementconsists of a compressible porous structure polymeric foam filterelement 1 overmoulded onto or joined to a polymeric or metallic tube orspring or other hollow support element 2. The foam filter element 1 iscompressed into a housing or pod 3 at a distal end of a catheter 6 toadvance it to the required location. Once in situ the housing 3 iswithdrawn or the filter element 1 is advanced. This action allows thecompressed filter element 1 to expand to the required size and occlude ablood vessel 4 except for the path or paths provided through the fitterelement 1. The filter element 1 is designed to provide a pathway ormultiple pathways through for blood cells and other blood constituentsbut to capture emboli of a size greater than the filter pore size. Bloodflow rate is maintained by forming the filter element such that a localpressure drop across the filter is minimised. The filter element 1 has aproximal inlet end 7 and a distal outlet end 8. The inlet end 7 has aplurality of inlet openings sized to allow blood and embolic materialenter the filter element. The outlet end 8 has a plurality of outletopenings sized to allow through passage of blood but to retain undesiredembolic material within the body of the filter element 1.

The filter element 1 in this case is of a porous structure or polymericfoam which has a open cell structure with a typical density less than400 kg per cubic meter. Preferably the density will be less than 100 kgper cubic meter and ideally will be less than 50 kg per cubic meter. Thefilter properties may be achieved through appropriately sizing the poresof the foam body or additionally by removing material to createappropriately sized pathways for blood to flow through and means ofcapturing larger sized particles. A number of configurations for thiswill be described that can tailor both the sizing and flow ratecharacteristics of the filter element 1 either independently orsimultaneously. The actuation and deployment of the filter element 1 areachieved by providing relative motion between the filter element 1 andthe covering housing 3.

It is not desirable that the catheter moves relative to the supportelement 2 during manipulation. Motion may be prevented by fixing theinner support element 2 to the catheter 6 in a number of different ways.In the embodiment described this is achieved by way of having a catheter6 covering the support element 2 and filter element 1 to which it isfixed. As illustrated in FIGS. 3A and 38 the fixing may be achieved bymeans of a shrink wrap tube 5 that is shrunk to capture both thecovering catheter 6 and the inner support element 2. Once the filterelement 1 is in the desired position, the shrink-wrap joint is brokenusing the peel-away tab 7 to allow the outer catheter 6 to be removedproximally and leave the support element 2 and filter element 1 inplace.

A number of other workable arrangements could be used to join thesupport element 2 and catheter 6. A split collar arrangement 10 (FIGS. 4& 5) could be used that was removable by means of unlocking a screw or anumber of screws or an arrangement such as a jubilee clip 11 (FIGS. 6 &7) which could be loosened to free the bond between the components.

Another method that could be used to temporarily fix the inner supportelement 2 to the outer sheath or catheter 6 is a Hemostasis HighPressure Touhy Borst Y adapter. This commercially available adapter isneeded to enable the physician to flush the sheath before being insertedinto the artery. The outer sheath or catheter may be permanentlyattached to this adapter. The inner tubular support element 2 runsthrough the Touhy Borst section of the adapter and thus through thecentre of the sheath. Tightening the Touhy Borst section releases thisgrip, thus allowing the inner tubular support element 2 and the outersheath to move relative to each other once again.

The design of the filter element 1 is shown in a typical embodiment inFIG. 8, where a foam substrate filter body has material removed tocreate a series of channels or pathways 20 for the blood to flow throughbut which would cause a restriction for embolic material to prevent itgoing through the filter. The pathways 20 may be machined using avariety of methods such as laser cutting with excimer, YAG, CO2, orother laser type, freezing and machining or lost wax machining. A numberof arrangements are possible with the sizing reflective of therequirements. In the configuration shown, the inlet holes are preferably0.5 mm or greater in size to capture large emboli while the outlet holesare less than 300 microns. These can be easily varied as required tofilter differing sized particles from a variety of fluid media in avariety of vessel sizes.

The filter media can be bonded to the tubing substrate by way of avariety of available technologies such as mechanical, solvent oradhesive bonding and overmoulding in an arrangement such that thesubstrate is placed in the mould and the polymer material is then shotinto the mould and forms a bond at the interface between the substrateand the polymer element. Additionally, the foam or porous element couldbe extruded onto or bonded to a substrate.

It will be noted that the filter element 1 has a rounded distal end 21to facilitate insertion and the proximal end 22 is tapered to facilitatewithdrawal. Alternatively, as illustrated in FIG. 9 the distal end 23may be tapered.

Referring particularly to FIG. 10 at the end of the interventionalprocedure, the device can be withdrawn by means of advancing a largebore catheter 25 to the proximal end 22 of the filter 1 and pulling thefilter 1 into the catheter 25. The filter 1 will compress and seal theproximal filter inlet openings after the initial taper is drawn into thecatheter 25 before collapsing the rest of the filter body. Once thefilter 1 has been withdrawn fully into the catheter 25 it can then bereadily removed from the patient. The filter 1 will contain the capturedemboli.

In another embodiment of the invention as illustrated in FIGS. 11 to 15,an arrangement of spokes 30 covered with a membrane or porous fabric ormesh 31 can be folded down into a delivery sheath or pod for subsequentdeployment in the target vessel. The design consists of a substrateshaft 33 onto which are radially or circumferentially bonded a series ofpre-shaped wires 30. The wires 30 are joined on the proximal end into amovable collar or tube 32 mounted on the substrate shaft 33 and at thedistal end into a fixed tube 34. The tube 32 can move proximally anddistally to the extent that it will open and close the assembly in amanner similar to an umbrella and thereby occlude the vessel. The spokes30 may be fabricated in a range of metallic, polymeric and compositematerials. The frame is covered with a porous material 31, whose poresize is selected to allow the media through, effectively creating ascreen filter. The covering fabric 31 could be bonded to the frame 30 bymeans of casting a material such as a polyurethane or PET onto thepre-formed shape. The film may then be lazed or made porous by othermeans such as mechanical or heat punching or by chemical etching.Additionally, incorporating a soluble particle in the polymer matrix,subsequent removal of the particle would render the polymer porous.Control of porosity is achieved by tailoring the ratio and distributionof the particulate within the polymer matrix.

When the assembly is configured longitudinally a sheath or pod may beslid over it to cover it. As with the previous embodiment, the loadedcatheter is positioned in the required location by threading it over theguidewire. Once the desired location has been reached, the sheath may bemoved back and allow the assembly be exposed in the vessel. A sleeve 35can then be moved forward to open or deploy the assembly. The relativesizing and choice of materials operates such that the sleeve 35 will notslide on the inner tubing unless an external force is applied to moveit. When deployed, the device will remain open and catch whateverembolic material is moving towards the brain. At the end of theprocedure, a pre-shaped component advanced over the inner tube will dockwith the movable tube 32 and allow it to be slid towards the proximalend of the device with the result that the structure is closed. A largersheath can then separately be advanced to the site of the filter and thefilter may be pulled or manipulated proximally into it. When withdrawninto the sheath or catheter, the device may then be removed either overthe guidewire or with it.

Referring to FIGS. 16 and 17 there is illustrated another embolicprotection device. In this case the filter element has a design based ona shaped thin film component bonded onto the tubing substrate. A widenumber of shapes could be made to work in the application. An elementwhich through it's preshaped form will open into a framework 40 when therestraining force is removed is attached to a tubing substrate 41. Theframe element 40 can be manufactured from a range of metallic orpolymeric components such as a shape memory alloy like Nitinol or ashape memory polymer or a shaped stainless steel or metal with similarproperties that will recover from deformation sufficiently to cause thefilm component to open. Otherwise a mechanical movement or actuation cancause the device to open. The shaped film component is attached over theframe 40. The film component can be formed by a number of knowncommercial technologies. These include blow-moulding, dip casting,solution casting, spin casting and film welding as well as adhesivejoining. The object is to produce a formed shape that can be opened inthe vessel to a size and shape to occlude it. Filtration is achieved bycreating a pattern or series of openings in the proximal and distal endsof the element that allows emboli and blood to enter the device buthaving a range of smaller openings in the distal end to allow the bloodto pass through to the distal vasculature while retaining the emboli.

While being delivered to the required site, the filter element iscovered or restrained by a sheath. By withdrawing the sheath oradvancing the filter device, the filter is uncovered and opens toocclude the vessel. During the procedure, the filter acts to capture allembolic material that attempts to flow distally. At the end of theprocedure, a sheath is advanced to the proximal end of the device andthe filter is pulled proximally into it with the retained embolicaptured. In this design configuration, the emboli can easily be removedfor analysis afterwards.

The invention above is described as it relates to a device that can beused over a medical guidewire. The opportunity exists to configure theinvention in a manner that it could in itself be used as the primarycrossing device. All of the filter designs described above could bemounted onto either the over the wire or the primary crossing device asdescribed hereunder. For a primary crossing device the filter would bebonded to a solid substrate. Some benefits would accrue in that theinner diameter onto which the filter could be wrapped down would besmaller because it would not need to move over another instrument. FIG.18 illustrates the differences involved. The filter element 1 is mountedon the substrate shaft 33. A collapsible filter support element 50 ismounted on the substrate shaft 33 at a proximal end of the filter 1. Thesupport element 50 has a number of foldable arms 51 which collapseagainst the shaft 33 for deployment and upon release extend outwardly toexpand the filter 1 in the vessel.

Referring to FIGS. 20 to 22 there is shown alternative constructions offilter element comprising a compressible filter 1 shown in an expandedposition with a large inlet opening 60 and smaller outlet openings 61. Acollapsible wire support 62 is provided at a proximal end of the filter1. The wire support 62 is collapsible with the filter 1 within a housingor pod for deployment and upon release expands to support the filter 1in the vessel 4.

An alternative filter arrangement is shown in FIGS. 23 to 27. In thiscase, the filter comprises a Nitinol mesh which is expandable from acollapsed position shown in FIG. 23 for deployment to an expanded in useposition shown in FIG. 27 to provide a filter body 65 with proximalinlet 66 and distal outlets 67.

For a primary crossing device, the distal end of the device will beflexible and atraumatic. This can be achieved by a number of means suchas fabricating a spring or polymeric element to be flexible enough todeflect when it comes into contact with the walls of the vessel. The tipsection would be mounted distally to the filter element. An intermediatesection of the device will house the filter 1 which would be coveredprior to deployment. A sheath could be fully the length of the device orattached by an actuator to a shorter sheath that covers the filter only.The proximal section of the device will provide a platform for theballoon dilatation and stent devices. The provision of a platform may beachieved as shown by removing the proximal covering to expose a wire orspring assembly. Alternatively, the whole proximal section couldfunction as the platform. Essentially, to function as the platform forballoon catheter and stent, the devices should be sized with an outsidediameter dimension that allows free movement of the catheter systemsover it. Typical industry standards for coronary products permit freemovement of devices over a 0.014″ or 0.018″ diameter while peripheralangioplasty applications use a 0.035″ OD.

Referring to FIG. 28 the tubing substrate 33 onto which the filterelement is bonded can move between two stoppers 63 and 64, the stoppersare mounted on the primary crossing guidewire 2. The stoppers can bemanufactured from a range of metallic or polymeric components, whichwill permit movement of the tubing substrate 33 between them. Thestoppers may also be in the form of a step in the actual medicalguidewire. A large variation in distances between stoppers 63 and 64could be made to work in this application. The stoppers are sized toprevent movement of the tubing substrate either over or under them sothat they act as a stop position for the tubing substrate in both theirproximal and distal locations. The stoppers can be mounted onto theprimary crossing guidewire by a number of known commercial technologies;these include soldering, welding, braising, crimping and adhesivebonding. The proximal stopper will be small enough in size to fit intothe internal shaft of the delivery catheter. The filter element can moveaxially and rotationally independently of the guidewire. This allows forgood wire movement and control of filter position. The filter positionwill be maintained during the exchange of catheters. Any commerciallyknown available guidewire can be adapted accordingly and used with thistechnique.

FIG. 29 refers to an “olive” 65; the olive component can be manufacturedfrom a range of metallic or polymeric components such as polymericfoams, plastics, stainless steel or metal. The olive will allow a smoothtransition between the guidewire 2 and the pod 3 into which the filterelement is loaded and also allows for easy positioning of the filterelement within the pod. The olive can be directly attached to theguidewire or it may also be attached to a tubing substrate 33. The olivecan be attached to the guidewire or tubing substrate by a range of knowntechniques such as adhesive bonding and soldering. The olive will workas required for a range of distances distal to the filter element. Awide number of shapes and sizes could be made to work as the olivecomponent.

FIG. 30 refers to the filter element 1 when it is positioned in its mostdistal position. The filter element may achieve this position duringloading or after deployment. The stopper element 64 prevents the filterelement 1 from moving beyond it in the distal direction.

FIG. 31 illustrates the filter element in its most proximal location thefilter element may achieve this position when deploying the device orafter deployment. The stopper element 63 prevents the filter element 1from moving beyond it in the proximal direction.

FIG. 32 refers to a floating distal tip in this case a stopper component66 is placed proximal to the distal end of the filter. The most distalend of the filter being fixed to a marker band 70 or other suitablesubstrate. The marker band 70 is not fixed to the substrate tubing 33.This allows the distal end of the filter freedom of movement in theaxial direction beyond the stopper component. The stopper component canbe made to work using any shape or form so as to prevent movement of thedistal end of the filter in the proximal direction beyond the point offixturing of the stopper component. The stopper component may bemanufactured from metals or polymeric material, it can be joined to thetubing substrate 33 by a number of existing technologies includingadhesive bonding and soldering. The stopper component 66 will work whenplaced in any location between 50 and 70. A floating distal tip on thefilter element will facilitate the loading of the filter element intothe loading pod as the filter can now is extend in the axial directionand therefore be wrapped down over a greater length. This will reducethe loading force required and also reduce the profile of the loadedfilter. The floating distal tip design will facilitate the loading of alarge range of filter designs.

FIG. 33 refers to a concertina shaped filter with a floating distal tip.This filter geometry adds to the circumferential integrity of the filterand thus prevents the formation of creases along the length of thefilter. “A” illustrates the filter as it will be when in position. “B”illustrates how the distal tip will extend in the axial direction whenthe filter element is loaded into a loading pod. The floating tip designcan be used to accommodate the loading of many filter shape designs. Forthe filter design shown a longer pod is needed to accommodate theincrease in axial length of the filter element when loaded.

FIG. 34 refers to the floating distal tip design with a spring element67 incorporated into the design. The spring is placed distal to thefilter element. As previously illustrated in FIG. 33, the floatingdistal tip extends in the axial direction when loaded, the spring actsas a safety device when the filter is deployed and ensures the return ofthe floating distal tip to its primary location. The spring element willbe soft enough to allow the distal tip to extend freely in the distaldirection during loading but stiff enough to push the distal tip back toits primary location after deployment. The spring element can bemanufactured from either a polymeric or metal component. The springelement can be mounted onto a substrate 33 and a stopper component usedto prevent axial movement of the spring in the distal direction. Othermethods of keeping the distal end of the spring element stationary couldbe used such as bonding, welding, crimping, soldering or crimping thedistal end of the spring onto the substrate 33. This technique couldalso be made to work with the spring being part of the actual guidewire.There are many other configurations by which a return spring element maybe incorporated into the filter as shown in FIGS. 35 and 36.

In FIG. 35 the spring element 67 is bonded to the substrate 33 at itsproximal end and the distal end of the filter element is bonded to thespring shaft. This design allows the distal end of the filter element toextend in the distal direction. The extension length could be determinedby either the positioning of a stopper 68 or the stiffness of thespring. When external forces are removed from the filter the spring willreturn the filter to its primary location. In FIG. 36 a shape memoryalloy such as nitinol is used to return the filter to its primarylocation. The nitinol support frame 69 is fixed to the substrate 33 atits proximal end 70 and is floating at the distal end 71. The shapememory properties of the nitinol will ensure that the filter elementreturns to its primary location. This design can facilitate the use ofany other commercially available or known shape memory alloys. Thisdesign could also be made to work using a spring component.

FIG. 37 again incorporates the floating distal tip design. The filterbody 65 as previously illustrated in FIG. 27 is mounted onto a substrate33. At the proximal end the stent is fixed to the substrate. Thefloating distal tip design allows the filter body 65 to extend in thedistal direction. As the filter body 65 extends there is a reduction inits outside diameter and an Increase in its overall length. There may ormay not be need for a stopper 68 as the filter body 65 will extend up toits own elastic limit which is determined by its size and geometry. Theshape memory function of the filter body 65 will cause the distal tip toreturn to its primary location when external forces are removed from it.The proximal end of the filter body 65 may be fixed to the substrate bya number of known technologies such as bonding, soldering or crimping.

FIG. 38 illustrates a number of different filter designs which could bemade to work as embolic protection devices. These filter designs allwork to reduce the longitudinal length of creases which may occur shouldthe filter be oversized, therefore acting as crease breakers. Eitherends of the filters shown could act as both proximal and distal ends forthe filter. The filter body may be tubular or frusto-conical.

Referring to FIGS. 40 to 42 there is illustrated an embolic protectiondevice according to the invention indicated generally by the referencenumber 100. The device 100 has a guidewire 101 with a proximal end 102and a distal end 103. A tubular sleeve 104 is slidably mounted on theguidewire 101. A collapsible filter 105 is mounted on the sleeve 104,the filter 105 being movable between a collapsed stored position againstthe sleeve 104 and an expanded position as shown in the drawingsextended outwardly of the sleeve 104 for deployment in a blood vessel.

The sleeve 104 is slidable on the guidewire 101 between a pair ofspaced-apart end stops, namely an inner stop 106 and an outer stop whichin this case is formed by a spring tip 107 at the distal end 103 of theguidewire 101.

The filter 105 comprises a mesh net 110 mounted over a collapsiblesupport frame 111. The mesh net 110 is gathered into the sleeve 104 ateach end, the net 110 being rigidly attached to a proximal end 112 ofthe sleeve 104 and the net 110 being attached to a collar 115 which isslidable along a distal end 114 of the sleeve 104. Thus the distal endof the net 110 is longitudinally slidable along the sleeve 104. Thesupport frame 111 is also fixed at the proximal end 112 of the sleeve104. A distal end 116 of the support frame 111 is not attached to thesleeve 104 and is thus also free to move longitudinally along the sleeve104 to facilitate collapsing the support frame 111 against the sleeve104. The support frame 111 is such that it is naturally expanded asshown in the drawings and can be collapsed inwardly against the sleeve104 for loading in a catheter 118 or the like.

The filter 105 has large proximal inlet openings 117 and small distaloutlet openings 119. The proximal inlet openings 117 allow blood andembolic material to enter the filter body, however, the distal outletopenings 119 allow through passage of blood but retain undesired embolicmaterial within the filter body.

An olive guide 120 is mounted at a distal end of the sleeve 104 and hasa cylindrical central portion 121 with tapered ends 122,123. The distalend 122 may be an arrowhead configuration for smooth transition betweenthe catheter and olive surfaces. The support frame 111 is shaped toprovide a circumferential groove 125 in the filter net 110. If thefilter is too large for a vessel, the net may crease and this groove 125ensures any crease does not propagate along the filter.

Enlarged openings are provided at a proximal end of the filter net 110to allow ingress of blood and embolic material into an interior of thenet 110.

In use, the filter 105 is mounted in a collapsed state within a distalend of the catheter 118 and delivered to a deployment site. When thefilter is correctly positioned the catheter 118 is retracted allowingthe support frame 111 to expand inflating the net 110 across the vesselin which the filter is mounted. Blood and emboli can enter the enlargedopenings at a proximal end of the net 110. The blood will pass throughthe net wall, however, the openings or pores in the net are sized so asto retain the embolic material. After use the catheter is deliveredalong the guidewire 101 and slid over the filter 105 engaging theproximal inlet end 112 first to close the openings and then graduallycollapsing the net against the sleeve 104 as the catheter 118 advancesover the filter 105. Once the filter 105 is fully loaded in the catheter118, it can then be withdrawn.

It will be noted that a proximal end of the filter is fixed and a distalend of the filter is longitudinally movable along the sleeve tofacilitate collapsing of the filter net.

Further, the catheter engages the proximal end of the filter net firstthus closing the filter net inlet and preventing escape of embolicmaterial from the filter net as the filter net is being collapsed.

Conveniently the tip of the catheter which forms a housing or pod forreception of the filter is of an elastic material which can radiallyexpand to accommodate the filter with the captured embolic material. Bycorrect choice of material, the same catheter or pod can be used todeploy and retrieve the filter. For deployment, the elastic materialholds the filter in a tightly collapsed position to minimise the size ofthe catheter tip or pod. Then, when retrieving the fitter, the cathetertip or pod is sufficiently elastic to accommodate the extra bulk of thefilter due to the embolic material.

Also, the filter is not fast on the guidewire and thus accidentalmovement of the guidewire is accommodated without unintentionally movingthe filter, for example, during exchange of medical devices or whenchanging catheters.

It will also be noted that the filter according to the invention doesnot have a sharp outer edge as with many umbrella type filters. Rather,the generally tubular filter shape is more accommodating of the interiorwalls of blood vessels.

Conveniently also when the filter has been deployed in a blood vessel,the catheter can be removed leaving a bare guidewire proximal to thefilter for use with known devices such as balloon catheter and stentdevices upstream of the filter.

1. A vascular filtration device for removing embolic material in bodyfluid flowing within a vessel, the vascular filtration device having apre-deployment state for delivery to a treatment site and a deploymentstate for filtering the body fluid flowing within the vessel,comprising: a guidewire having a longitudinal axis; and a filterassembly comprising: a tubular member, the guidewire extending throughthe tubular member and being rotatable and axially slidable relative tothe tubular member; a filter coupled to the tubular member, the filterhaving at least one inlet opening provided towards a proximal end of thefilter and a plurality of outlet openings, the outlet openings allowingthe body fluid to flow through the filter but retaining embolic materialwithin the filter, and the inlet opening being larger than any of theoutlet openings; a filter frame attached to the tubular member, thefilter frame coupled to the filter in the deployment state to maintainthe inlet opening open, the filter frame being collapsed towards theguidewire in the pre-deployment state; in the deployment state thecenter of the inlet opening being offset from the longitudinal axis ofthe guidewire; and in the deployment state, rotation or distaltranslation imparted to the guidewire is not imparted to the filter. 2.The device according to claim 1 wherein the inlet opening is a singlefluid inlet.
 3. The device according to claim 1 wherein the inletopening of the filter in the deployment state is angled toward a distalend of the filter.
 4. The device according to claim 1 wherein the filterframe is at a proximal end of the filter.
 5. The device according toclaim 1 wherein the filter frame is made from a shape memory material.6. The device according to claim 5 wherein the filter frame is made fromNitinol wire.
 7. The device according to claim 1 wherein the filterframe is made from Nitinol.
 8. The device according to claim 1 whereinthe filter frame is made from wire.
 9. The device according to claim 1wherein the filter comprises a mesh.
 10. The device according to claim 1wherein the filter comprises Nitinol mesh.
 11. The device according toclaim 1 which further comprises a delivery member for the filterassembly, wherein the filter frame and the filter are collapsed withinthe delivery member during the pre-deployment state, and upon releasefrom the delivery member, the deployed filter frame supports the filter.12. The device according to claim 11 which further comprises a retrievalmember for removing the filter assembly, wherein the retrieval membercovers at least a portion of the filter and permits the filter and theretained embolic material to be retrieved from the vessel.
 13. Thedevice according to claim 12 wherein a single member is both thedelivery member and the retrieval member.
 14. The device according tothe claim 12 wherein the retrieval member comprises a pod for thereception of the filter.
 15. The device according to claim 11 whereinthe delivery member comprises a pod for the reception of the filter. 16.The device according to claim 1 comprising a proximal tubular member anda distal tubular member, the tubular members being spaced-apart alongthe longitudinal axis of the guidewire.
 17. The device according toclaim 16 wherein the distal tubular member comprises a radiopaque markerband.
 18. The device according to claim 1 further comprising a stop tolimit the extent of axial movement of the tubular member relative to theguidewire.
 19. The device according to claim 18 wherein the stop islocated distally of the proximal end of the filter.
 20. The deviceaccording to claim 19 wherein the stop is located proximally of thedistal end of the filter.
 21. A vascular filtration device for removingembolic material in body fluid flowing within a vessel, the vascularfiltration device having a pre-deployment state for delivery to atreatment site and a deployment state for filtering the body fluidflowing within the vessel, comprising: a guidewire having a longitudinalaxis; and a filter assembly comprising: a tubular member, the guidewireextending through the tubular member and being rotatable and axiallyslidable relative to the tubular member; a filter coupled to the tubularmember, the filter having a single inlet opening provided towards aproximal end of the filter and a plurality of outlet opening, the outletopenings allowing the body fluid to flow through the filter butretaining embolic material within the filter, and the inlet openingbeing larger than any of the outlet openings; a wire frame coupled tothe filter in the deployment state to maintain the inlet opening open,the wire frame being collapsed towards the guidewire in thepre-deployment state; in the deployment state the center of the inletopening being offset from the longitudinal axis of the guidewire; and inthe deployment state, rotation or distal translation imparted to theguidewire is not imparted to the filter.
 22. The device according toclaim 21 comprising a proximal tubular member and a distal tubularmember, the tubular members being spaced-apart along the longitudinalaxis of the guidewire.
 23. The device according to claim 21 furthercomprising a stop to limit the extent of axial movement of the tubularmember relative to the guidewire.
 24. The device according to claim 23wherein the stop is located distally of the proximal end of the filter.25. The device according to claim 24 wherein the stop is locatedproximally of the distal end of the filter.
 26. The device according toclaim 23 wherein the stop is located proximally of the distal end of thefilter.
 27. The device according to claim 21 wherein the distal tubularmember comprises a radiopaque marker band.
 28. A vascular filtrationsystem for removing embolic material in body fluid flowing within avessel, the vascular filtration system having a pre-deployment state fordelivery to a treatment site and a deployment state for filtering thebody fluid flowing within the vessel, comprising: a guidewire having alongitudinal axis; a filter assembly comprising: a tubular member, theguidewire extending through the tubular member and being rotatable andaxially slidable relative to the tubular member; a filter coupled to thetubular member, the filter having at least one inlet opening providedtowards a proximal end of the filter and a plurality of outlet opening,the outlet openings allowing the body fluid to flow through the filterbut retaining embolic material within the filter, and the inlet openingbeing larger than any of the outlet openings; a filter frame coupled tothe filter in the deployment state to maintain the inlet opening open,the filter frame being collapsed towards the guidewire in thepre-deployment state; in the deployment state the center of the inletopening being offset from the longitudinal axis of the guidewire; in thedeployment state, rotation or distal translation imparted to theguidewire is not imparted to the filter; a delivery member for thefilter assembly, wherein the filter frame and the filter are collapsedwithin the delivery member during the pre-deployment state, and uponrelease from the delivery member, the deployed filter frame supports thefilter; and a retrieval member for removing the filter assembly, whereinthe retrieval member covers at least a portion of the filter and permitsthe filter and the retained embolic material to be retrieved from thevessel; a single member being both the delivery member and the retrievalmember.
 29. The system according to claim 28 comprising a proximaltubular member, and a distal tubular member, the tubular members beingspaced apart along the longitudinal axis of the guidewire.
 30. Thesystem according to claim 28 further comprising a stop to limit theextent of axial movement of the tubular member relative to theguidewire.
 31. The system according to claim 30 wherein the stop islocated distally of the proximal end of the filter.
 32. The systemaccording to claim 31 wherein the stop is located proximally of thedistal end of the filter.
 33. The system according to claim 30 whereinthe stop is located proximally of the distal end of the filter.
 34. Thesystem according to claim 28 wherein the distal tubular member comprisesa radiopaque marker band.